Position determining method and system using surveillance ground stations

Abstract

An aircraft avionics system and method for automatically determining an aircraft position. The system and method determine distances to UAT ground stations based on timing signals in transmissions from the UAT ground stations and determines one or more possible positions for the aircraft at which the aircraft is at the determined distances from respective UAT ground stations. The system and method may use three or more UAT ground stations to reduce the possible positions for the aircraft to a single possible position. The system and method also may use dead reckoning or VOR or ADF signals to reduce the possible positions for the aircraft to a single possible position. The system and method may also determine the position of an aircraft by determining true bearings to SSR ground stations and determining the possible positions for the aircraft at which the aircraft is at respective bearings to each SSR ground station.

1 . A computer system for determining aircraft position comprising:
 a clock onboard an aircraft;   an antenna onboard the aircraft configured to receive UAT ground station transmissions;   a database containing locations of UAT ground stations; and   a computer processor onboard the aircraft, in communication with the clock, the antenna, and the database, the computer processor configured to:
 receive transmissions from at least two UAT ground stations; 
 identify each of the at least two UAT ground stations based on information from the UAT ground station transmissions; 
 extract from the database locations of each of the at least two UAT ground stations; 
 compare timing signals from each of the at least two UAT ground stations to determine a distance of the aircraft from each of the at least two UAT ground stations; and 
 determine at least one location at which the aircraft is at the determined distance from each of the at least two UAT ground stations. 
   
     
     
         2 . The system of  claim 1  wherein the computer processor outputs the determined at least one aircraft location to an ADS-B system of the aircraft. 
     
     
         3 . The system of  claim 1  wherein the computer processor identifies at least three UAT ground stations; and
 wherein the computer processor determines a single location at which the aircraft is at the determined distanced from each of the at least three UAT ground stations. 
 
     
     
         4 . The system of  claim 1  wherein the computer processor is further configured to use dead reckoning from a previous known position of the aircraft to determine a single aircraft location from the at least one location at which the aircraft is at the determined distance from each of the at least two UAT ground stations. 
     
     
         5 . The system of  claim 1  further comprising at least one of a VOR receiver and an ADF receiver; and
 wherein the computer processor is further configured to use at least one of VOR and ADF signals to determine a single aircraft location from the at least one location at which the aircraft is at the determined distance from each of the at least two UAT ground stations. 
 
     
     
         6 . A computer-implemented method for determining an aircraft position comprising:
 receiving at least two UAT ground station transmissions, each UAT ground station transmission including a timing signal;   comparing each received timing signal to an onboard timing signal to determine a distance to each UAT ground station; and   based on known locations of each UAT ground station, determining at least one aircraft location at which the aircraft is at the determined distance from each of the at least two UAT ground stations.   
     
     
         7 . The computer-implemented method of  claim 6  further comprising outputting the determined at least one aircraft location to an ADS-B system. 
     
     
         8 . The computer-implemented method of  claim 6  wherein receiving at least two UAT ground station transmissions comprises receiving at least three UAT ground station transmissions; and
 determining a single location at which the aircraft is at the determined distanced from each of the at least three UAT ground stations. 
 
     
     
         9 . The computer-implemented method of  claim 6  further comprising dead reckoning from a previous known position of the aircraft to determine a single aircraft location from the at least one location at which the aircraft is at the determined distance from each of the at least two UAT ground stations. 
     
     
         10 . The computer-implemented method of  claim 1  further comprising using at least one of VOR and ADF signals to determine a single aircraft location from the at least one location at which the aircraft is at the determined distance from each of the at least two UAT ground stations. 
     
     
         11 . A computer system for determining aircraft position comprising:
 a compass onboard an aircraft;   a directional antenna onboard the aircraft configured to receive SSR ground station transmissions;   a database containing locations of SSR ground stations; and   a computer processor onboard the aircraft, in communication with the compass, the directional antenna, and the database, the computer processor configured to:
 receive transmissions from at least two SSR ground stations; 
 identify each of the at least two SSR ground stations based on information from the SSR ground station transmissions; 
 extract from the database locations of each of the at least two SSR ground stations; 
 determine a true bearing to each of the at least two SSR ground stations; and 
 determine at least one location at which the aircraft is at the determined bearing to each of the at least two SSR ground stations. 
   
     
     
         12 . The system of  claim 11  wherein the computer processor outputs the determined at least one aircraft location to an ADS-B system of the aircraft. 
     
     
         13 . The system of  claim 11  wherein the computer processor is further configured to use dead reckoning from a previous known position of the aircraft to determine a single aircraft location from the at least one location at which the aircraft is at the determined distance from each of the at least two SSR ground stations. 
     
     
         14 . The system of  claim 11  further comprising at least one of a VOR receiver and an ADF receiver; and
 wherein the computer processor is further configured to use at least one of VOR and ADF signals to determine a single aircraft location from the at least one location at which the aircraft is at the determined distance from each of the at least two SSR ground stations. 
 
     
     
         15 . A computer-implemented method for determining an aircraft position comprising:
 receiving at least two SSR ground station transmissions;   determining a true bearing to each of the at least two SSR ground stations; and   based on known locations of each SSR ground station, determining at least one aircraft location at which the aircraft is at the determined distance from each of the at least two SSR ground stations.   
     
     
         16 . The computer-implemented method of  claim 15  further comprising outputting the determined at least one aircraft location to an ADS-B system of the aircraft. 
     
     
         17 . The computer-implemented method of  claim 15  further comprising using dead reckoning from a previous known position of the aircraft to determine a single aircraft location from the at least one location at which the aircraft is at the determined distance from each of the at least two SSR ground stations. 
     
     
         18 . The method of  claim 15  further comprising using at least one of VOR and ADF signals to determine a single aircraft location from the at least one location at which the aircraft is at the determined distance from each of the at least two SSR ground stations. 
     
     
         19 . A computer-implemented method for determining an aircraft position, comprising:
 receiving at least three SSR ground station transmissions;   determining locations of the at least three SSR ground stations;   determining relative bearings from the aircraft to each of the respective at least three SSR ground stations;   determining a size and location of a first circle that includes on its circumference the aircraft and a first SSR ground station and a second SSR ground station of the at least three SSR ground stations;   determining a size and location of a second circle that includes on its circumference the aircraft and the first SSR ground station and a third SSR ground station of the at least three SSR ground stations; and   determining a first intersection of the circumferences of the first and second determined circles as a location at which the aircraft is located.   
     
     
         20 . The computer-implemented method of  claim 19  wherein determining an intersection of the circumferences of the first and second determined circles at which the aircraft is located includes determining two intersection points and selecting as the location of the aircraft one of the two intersection points located farthest from the first SSR ground station. 
     
     
         21 . The computer-implemented method of  claim 19  further comprising determining a size and location of a third circle that includes on its circumference the aircraft and the second SSR ground station and the third SSR ground station of the at least three SSR ground stations;
 determining a second intersection of the circumferences of the first and third determined circles as a location at which the aircraft is located; 
 determining a third intersection of the circumferences of the second and third determined circles as a location at which the aircraft is located; and 
 calculating as the location of the aircraft an average of the first, second, and third intersections. 
 
     
     
         22 . The computer-implemented method of  claim 19  further comprising determining a true bearing from the location at which the aircraft is located to one of the at least three SSR ground stations; and
 calculating the aircraft heading by comparing the determined true bearing to the relative bearing to the one SSR ground station. 
 
     
     
         23 . A computer system for determining aircraft position, comprising:
 a directional antenna onboard the aircraft configured to receive SSR ground station transmissions;   a computer processor onboard the aircraft, in communication with the directional antenna, configured to:
 receive transmissions from at least three SSR ground stations; 
 identify each of the at least three SSR ground stations based on information from the SSR ground station transmissions; 
 determine locations of the respective SSR ground stations; 
 determine a relative bearing to each of the at least three SSR ground stations; 
 determine a size and location of a first circle that includes on its circumference the aircraft and a first SSR ground station and a second SSR ground station of the at least three SSR ground stations; 
 determine a size and location of a second circle that includes on its circumference the aircraft and the first SSR ground station and a third SSR ground station of the at least three SSR ground stations; and 
 determine a first intersection of the circumferences of the first and second determined circles as a location at which the aircraft is located. 
   
     
     
         24 . The computer system of  claim 23  further including a database onboard the aircraft that includes locations of SSR ground stations; and
 wherein the computer processor determines locations of the respective SSR ground stations by associating each of the at least three identified SSR ground stations with a location in the database. 
 
     
     
         25 . The computer system of  claim 23  wherein each SSR ground station transmission includes a location of the SSR ground station; and
 wherein the computer processor determines locations of the respective SSR ground stations by extracting the location from the SSR ground station transmissions. 
 
     
     
         26 . The computer system of  claim 23  wherein the computer processor is further configured to:
 determine a size and location of a third circle that includes on its circumference the aircraft and the second SSR ground station and a third SSR ground station of the at least three SSR ground stations; and 
 determine a second intersection of the circumferences of the first and third determined circles as a location at which the aircraft is located; 
 determine a third intersection of the circumferences of the second and third determined circles as a location at which the aircraft is located; and 
 calculate as the location of the aircraft an average of the first, second, and third intersections. 
 
     
     
         27 . The computer system of  claim 23  wherein the computer processor is further configured to:
 determine a true bearing from the location at which the aircraft is located to one of the at least three SSR ground stations; and 
 calculate the aircraft heading by comparing the determined true bearing to the relative bearing to the SSR ground station. 
 
     
     
         28 . A computer-implemented method for determining an aircraft position comprising:
 in an aircraft, receiving transmissions from two SSR ground stations;   determining a relative bearing to each of the two SSR ground stations;   based on known locations of the two SSR ground stations and the relative bearings to each station, determining a set of possible positions of the aircraft; and   identifying a position from the set of possible positions at which the aircraft is located.   
     
     
         29 . The computer-implemented method of  claim 28  wherein identifying a position from the set of positions at which the aircraft is located comprises:
 determining a true bearing to each of the two SRR ground stations; and 
 determining a position from the set of positions closest to an intersection of lines defined by the true bearings to each of the two SSR ground stations as the position of the aircraft. 
 
     
     
         30 . The computer-implemented method of  claim 28  wherein identifying a position from the set of positions at which the aircraft is located comprises identifying a position closest to a dead reckoning position of the aircraft. 
     
     
         31 . The computer-implemented method of  claim 28  wherein the set of possible positions is a first set, and wherein identifying a position from the set of positions at which the aircraft is located comprises:
 receiving a transmission from a third SSR ground station; 
 determining a location of the third SSR ground station; 
 determining a relative bearing to the third SSR ground station; 
 based on the known locations of the first SSR ground station and the third SSR ground station, and based on the relative bearings to the first and third SSR ground stations, determining a second set of possible positions at which the aircraft may be located; 
 identifying a position from the first set of positions that is most proximate to a position from the second set of positions; and 
 identifying as the position of the aircraft a position based on the position from at least one of the first set of positions and the position from the second set of positions. 
 
     
     
         32 . The computer-implemented method of  claim 31  wherein identifying as the position of the aircraft a position based on the position from at least one of the first set of positions and the position from the second set of positions comprises identifying the position from the first set of positions as the position of the aircraft. 
     
     
         33 . The computer-implemented method of  claim 31  wherein identifying as the position of the aircraft a position based on the position from at least one of the first set of positions and the position from the second set of positions comprises identifying the position from the second set of positions as the position of the aircraft. 
     
     
         34 . The computer-implemented method of  claim 31  wherein identifying as the position of the aircraft a position based on the position from at least one of the first set of positions and the position from the second set of positions comprises identifying an average position between the position from the first set of positions and the second set of positions as the position of the aircraft. 
     
     
         35 . The computer-implemented method of  claim 28  wherein identifying a position from the set of positions at which the aircraft is located comprises identifying a position closest at least one of a VOR reading and an ADF reading.